Various constructions of heating devices, which use shearing forces to generate heat, are known in the art. Examples may be found in U.S. Pat. Nos. 5,778,843; 6,047,896 and 6,138,920. Among these, the latter illustrates a rather complicate control of an independent heating unit substantially separated from the conveyor drive for the tempering fluid. Shearing is mainly effected in a conical, smooth shearing gap, as is known for other purposes from agitator mills. Smooth are also the surfaces of a shearing arrangement according to U.S. Pat. No. 5,778,843 which shows also a unit separated from the fluid conveyor, and similar is the construction of U.S. Pat. No. 6,047,896. Ir. the two latter cases, electromagnets are provided for control purposes.
In contrast to the above-mentioned smooth shearing surfaces, individual shearing parts according to DE-198 51 546-A1 or U.S. Pat. No. 6,039,264 are provided with projections and recesses facing a smooth wall. In the DE-document, the projections and recesses in-between extend in axial direction, while in the U.S. patent, radial slots are formed. In both cases, the heating devices are also formed as parts substantially separated from the tempering fluid circulation which, of course, requires more space.
Document EP-0 826 530-A2 suggests assembling the conveyor arrangement for the tempering fluid together with a shearing forces using heat generator in a more compact form. In this document, these two units form themselves separated modules which are merely flanged together. Rather high expenses had to be spent for controlling the circulation of the tempering fluid from one module to the other one as for the circulation of the viscous liquid.
All these heating devices are often used in automobiles, but could also be applied in other spaces or vehicles, such as ships, planes, or even in the room of a house.